Vectorial diffraction of extreme ultraviolet light and ultrashort light pulses

In this thesis, we present applications in optics involving the diffraction theory of light for two advanced technologies. We have used a rigorous vectorial diffraction method to model: (i) the imaging of mask structures in extreme ultraviolet lithography, and (ii) ultrashort pulse propagation through small apertures. We have explained the chronological development of the method, the full derivation to implement the method, and we have also given several educational examples. Therefore, the method is not only a tool to calculate the effects but also to understand the physics behind the results. The first objective is to study the potential and challenges of the optical lithographic technique at the extreme ultraviolet wavelength region (at about Λ = 13.5 nm). We have investigated the application of the phase mask concept at this wavelength range, in order to increase the resolution (decrease the printed size) in the image plane of the projection system. Together with our optimised designs, the phase mask concept is necessary to be applied in the extreme ultraviolet lithography technique, when the desired image resolution becomes comparable to the dimension of the wavelength. In the discussion regarding our second objective, we have demonstrated that small slit apertures illuminated by the two fundamental polarisation modes (transverse electric and transverse magnetic) introduce polarisation-dependent dispersion effect that can be used for interesting applications. When using a double slit aperture, similar to the Young's double-slit experiment, the interference pattern resulting from the diffracted light from both slits can be properly explained. The interference pattern is influenced by several effects, i.e. the waveguiding effect of the slit that is polarisation-dependent, the diffraction by the slit aperture, and the generation of surface-bounded waves on the metal that appears for the transverse magnetic incident wave. The demonstrated high spatial and temporal information can be exploited for more advanced applications in optics, such as microscopy, spectroscopy, femtochemistry, etc.Applied Science

Near and intermediate fields of an ultrashort pulse transmitted through Young’s double-slit experiment

We present a systematic study of the transmitted field of an ultrashort pulse through Young’s double slit. We show how the spatial-temporal distribution of the field in the near and intermediate zone is affected by the input polarization state of the pulse. The analysis has been separated to study the dispersion, the diffraction and the interference effects individually. A combination of these effects provide the key to understand the temporal dependence of the field observed at various distinctive locations. A thorough understanding of the near- and intermediate-field distribution of a single- or double-slit for an ultrashort pulse can be exploited in many near-field applications, and tailored by tuning the width, thickness, and separation of the slits.Imaging Science and TechnologyApplied Science

Enhanced imaging in Extreme UV lithography by optimising the Molybdenum/Silicon thickness ratio in 2-D phase shifting mask design

Poster presentation Optics Research Group TU DelftOptics Research GroupApplied Science

Direct measurement of the near-field super resolved focused spot in InSb

Under appropriate laser exposure, a thin film of InSb exhibits a sub-wavelength thermally modified area that can be used to focus light beyond the diffraction limit. This technique, called Super-Resolution Near-Field Structure, is a potential candidate for ultrahigh density optical data storage and many other high-resolution applications. We combined near field microscopy, confocal microscopy and time resolved pump-probe technique to directly measure the induced sub-diffraction limited spot in the near-field regime. The measured spot size was found to be dependent on the laser power and a decrease of 25% (100nm) was observed. Experimental evidences that support a threshold-like simulation model to describe the effect are also provided. The experimental data are in excellent agreement with rigorous simulations obtained with a three dimensional Finite Element Method code.IST/Imaging Science and TechnologyApplied Science

Numerical analysis of a slit-groove diffraction problem

http://www.jeos.org/index.php/jeos_rp/article/view/07022We present a comparison among several fully-vectorial methods applied to a basic scattering problem governed by the physics of the electromagnetic interaction between subwavelength apertures in a metal film. The modelled structure represents a slit-groove scattering problem in a silver film deposited on a glass substrate. The benchmarked methods, all of which use in-house developed software, include a broad range of fully-vectorial approaches from finite-element methods, volume-integral methods, and finite-difference time domain methods, to various types of modal methods based on different expansion techniques